The present invention relates to the use of 2 -mercaptopyridine-1-oxide as an agent for removing silver from aqueous streams of suspensions and for recovering both the silver and the 2-mercaptopyridine-1-oxide. More particularly, the invention relates to a method for reclamation of silver as its halide and regeneration of 2-mercaptopyridine-1-oxide from aqueous suspensions of the silver salt of 2-mercaptopyridine-1-oxide.
Thus, the present invention is useful for the reclamation of silver in plants producing silver articles, for purifying effluent streams containing silver in preparation for disposal and for numerous other applications where it is desired to remove and/or recover silver from aqueous streams or suspensions thereof.
The heavy metal salts of 2-mercaptopyridine-1-oxide, including the silver salt thereof, are disclosed and claimed in Bernstein, U.S. Pat. No. 2,809,971. Their use as bactericides, fungicides and nematocides is also disclosed therein.
In the present invention the water insoluble silver salt of 2-mercaptopyridine-1-oxide which forms when 2-mercaptopyridine-1-oxide (including its soluble salts) is added to aqueous ionic silver containing systems provides a highly efficient mechanism for removal of silver. But to be of any commercial value, it must also be possible to regenerate 2-mercaptopyridine-1-oxide for reuse in the system or resale.